Fluxing agents comprising β-diketone and β-ketoimine ligands and a process for using the same

ABSTRACT

A residue-free fluxing process wherein the active fluxing agent comprises a β-diketone or β-ketoimine ligand. Such ligands react with surface metal oxides on workpieces to be soldered to form volatile metal-ligand complexes as reaction products which are sublimed from the surface leaving essentially no residue on the workpieces. The fluxing agents can be utilized in gas-phase processes wherein the workpieces are contacted with an effective amount of one or more ligands which are dispersed in a carrier gas or solvent or by incorporating the ligands into an alloy-vehicle mixture for use as conventional creams or pastes. The invention eliminates the need for post-reflow cleaning using solvents since no flux residue remains on the workpieces to be soldered following volatilization of the metal-ligand complex.

TECHNICAL FIELD

This invention relates to fluxing agents comprising an effective amountof a β-diketone or β-ketoimine ligand dispersed in a vehicle and aprocess for fluxing an article having at least a portion of a surfacecoated with a metal oxide.

BACKGROUND OF THE INVENTION

The reliability of modern electrical equipment is closely related to theefficacy of the soldering process used to connect the large number ofelectrical components making up the integrated circuit or electronicdevice. Wetting of the surfaces of the metal components to be joined isan essential prerequisite to the creation of a soldered joint.Sufficient wetting of the components to be joined can occur only if themetal oxides typically residing on the surface of the metals to bejoined are removed. Fluxing agents are typically employed to improve theefficiency of the soldering operation.

Three major types of fluxing agents are typically used wherein theselection of the particular type depends upon the particularapplication. The major types are water soluble fluxing agents, naturalrosins and activated rosins. Water soluble fluxes made from inorganicacids, organic acids, amine hydrohalides and the like, are reasonablyeffective in removing oxides from metal surfaces to be soldered buttypically leave a residue on the metal surfaces which may corrode theparts following soldering and impact the reliability of the apparatus.Moreover, the cleaning and removal of water soluble fluxes typicallycreates waste water disposal concerns. While hydrocarbon andchloro-fluorocarbon solvents can be used to remove the residue, suchsolvents are not totally effective and their use adds complexity andcost to the process as well as posing a potential threat to the Earth'senvironment.

Natural rosins typically do not contribute to the corrosion of thesoldered components but are somewhat weak in fluxing activity. Finally,activated rosins have a stability similar to natural rosins and do notcorrode the fluxed metal surfaces at room temperature. However, fullyactivated fluxing agents often generate corrosive gases at solderingtemperatures which can harm the substrate. Moreover, the residue of theactivated fluxing agents can combine with moisture to produce corrosiveacids which may shorten the life of the soldered joint. Solderingprocesses utilized in the production of microelectronic components suchas printed circuit boards typically utilize non-activated rosin fluxestreated with activators such as acids, bases and salts which typicallyleave a residue requiring a post-cleaning step to remove such harmfulresidues.

A cover gas wave soldering system marketed by Seitz & Hohnerlein (SEHO).Kreuzwertheim, West Germany, employs a fluxing agent comprising formicacid in admixture with a nitrogen cover gas. Formic acid, in thepresence of metals and metal oxides and at a temperature of about 150°C., breaks down into carbon dioxide and hydrogen wherein the reducingpower of the resultant hydrogen is added to the reducing power of theamino acid fluxing agent utilized.

A need exists for improved fluxing agents and processes for employingsuch fluxing agents in order to increase the reliability of the joiningoperation by promoting effective wetting of the solder to the workpieceprior to soldering and for reducing the incidence of post-solderingfailure due to corrosion and fatigue of the workpieces. Moreover,elimination of the post-cleaning step for removal of residue from thesoldered workpiece would greatly reduce processing costs and eliminatethe use of potentially environmentally hazardous solvents such aschloro-fluorocarbons.

SUMMARY OF THE INVENTION

The present invention relates to a residue-free soldering process andfluxing agents suitable for use in such a process wherein the fluxingagent comprises a β-diketone or β-ketoimine ligand dispersed in agaseous or liquid vehicle or paste. Such ligands react with surfacemetal oxides on workpieces to be soldered thereby forming volatilemetal-ligand complexes as reaction products which upon sublimation leaveessentially no residue on the workpieces to be soldered. The processcomprises contacting the portion of the article to be fluxed with aneffective amount of a fluxing agent comprising a β-diketone orβ-ketoimine ligand at a temperature sufficient to form a metal-ligandcomplex on the surface of the article to be fluxed and removing theresultant metal-ligand complex from the surface of the article bysublimation rendering the surface of the article substantially free ofthe metal species.

β-diketone and β-ketoimine ligands suitable for use in the claimedprocess are represented by the structural formula: ##STR1##

R₁ and R₃ are independently selected from a linear or branched alkyl oralkenyl group having from 1 to about 8 carbon atoms, each of which canoptionally be partially or fully fluorinated;

R₂ is a hydrogen atom, a linear or branched alkyl or alkenyl grouphaving from 1 to about 8 carbon atoms, each of which can optionally bepartially or fully fluorinated; and Y is selected from an oxygen atom;N-R₄ wherein R₄ is selected from an alkyl, aryl, aralkyl or hydroxyalkylgroup having from 1 to about 10 carbon atoms, each of which canoptionally be partially or fully fluorinated; or Y is ##STR2##

R₅, R₆ and R₇ are independently selected from a linear or branched alkylor alkenyl group having from 1 to about 8 carbon atoms, each of whichcan optionally be partially or fully fluorinated and

R₈ is a linear or branched alkylene, alkenylene, phenylene,alkylphenylene or hydroxyalkylene group having from 1 to about 8 carbonatoms, each of which can optionally be partially or fully fluorinated.

The above-mentioned formula I represents three distinct types of ligandswhich are each suitable for practicing the present invention. Each ofthe three types is characterized by the definition of the Y group. WhenY is an oxygen atom, the ligand is a β-diketone. When Y is N-R₃, theligand is a β-ketoimine ligand. Finally, when Y is represented byFormula II, the ligand comprises two β-ketoimines bridged by an organicfunctionality.

The above-mentioned ligands are typically suspended or admixed with acarrier or vehicle prior to contacting the region of the article to befluxed with an effective amount of the fluxing agent. Suitable carriersinclude gaseous and liquid vehicles such as argon, nitrogen, helium andperfluorinated hydrocarbons such as perhydrophenanthrene, solderingpastes and the like.

Process conditions for both the gaseous-phase and paste embodiments aresimilar to conventional reflow processes. Moreover, the fluxing agentcan be applied to workpieces to be soldered using a standing wave. or bydipping, brushing or spraying the workpieces to be soldered with thefluxing agent.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a fluxing agent and a process forutilizing the same wherein the fluxing agent comprises a β-diketone orβ-ketoimine ligand dispersed or mixed in a gaseous or liquid vehicle ora soldering paste or cream. Such ligands react with metal oxidesresiding on the surface of the workpieces to be soldered thereby formingvolatile metal-ligand complexes as reaction products which remove themetal oxide layer from the surface of the workpiece and which uponsublimation, leave essentially no residue on the surface of theworkpieces. The fluxing agent can be utilized in the gas-phase bycontacting the workpieces with one or more ligands suspended in a gasvehicle or by incorporating the ligands into a liquid or analloy-vehicle mixture for use as traditional creams or pastes,respectively. The invention eliminates the need for post-cleaning of theworkpieces following soldering and is believed to substantiallyeliminate corrosion and fatigue typically associated with conventionalprocesses wherein a residue remains on the workpieces following thefluxing and soldering operations.

The process for fluxing an article having at least a portion of asurface coated with a metal species comprises contacting the portion ofthe article to be fluxed with an effective amount of a β-diketone orβ-ketoimine ligand at a temperature sufficient to form a metal-ligandcomplex on the surface of the article to be fluxed and removing theresultant metal-ligand complex from the surface of the article bysublimation rendering the surface of the article substantially free ofthe surface coating.

The fluxing agents according to the present invention comprise aneffective amount of a β-diketone or β-ketoimine ligand admixed in avehicle or carrier. β-diketone and β-ketoimine ligands suitable forpracticing the present invention are represented by the formula:##STR3##

R₁ and R₃ are independently selected from a linear or branched alkyl oralkenyl group having from 1 to about 8 carbon atoms, each of which canoptionally be partially or fully fluorinated;

R₂ a hydrogen atom, a linear or branched alkyl or alkenyl group havingfrom 1 to about 8 carbon atoms, each of which can optionally bepartially or fully fluorinated; and

Y is selected from an oxygen atom; N-R₄ wherein R₄ is selected from analkyl, aryl, aralkyl or hydroxyalkyl group having from 1 to about 10carbon atoms, each of which can optionally be partially or fullyfluorinated; or Y is ##STR4##

R₅, R₆ and R₇ are independently selected from a linear or branched alkylor alkenyl group having from 1 to about 8 carbon atoms, each of whichcan optionally be partially or fully fluorinated and

R₈ is a linear or branched alkylene, alkenylene, phenylene,alkylphenylene or hydroxyalkylene group having from 1 to about 8 carbonatoms, each of which can optionally be partially or fully fluorinated.

Formula III represents three distinct types of ligands which are eachsuitable for practicing the process according to the present invention.Each of the three types is characterized by the definition of the Ygroup. When Y is an oxygen atom, the ligand is a β-diketone. When Y isN-R₃, the ligand is a β-ketoimine ligand. Finally, when Y is representedby the substituent presented in Formula IIIa, the ligand comprises twoβ-ketoimines bridged by an organic functionality.

The non-fluorinated, and partially or fully fluorinated β-diketoneligands suitable for use in the present process are represented by theformula: ##STR5##

R₁ and R₃ are independently selected from a linear or branched alkyl oralkenyl group having from 1 to about 8 carbon atoms, each of which canoptionally be partially or fully fluorinated; and

R₂ is selected from a hydrogen atom, or a linear or branched alkyl oralkenyl group having from 1 to about 8 carbon atoms, each of which canoptionally be partially or fully fluorinated.

The β-diketones represented by Formula III are prepared according tomethods well known in the art. In a preferred embodiment, R₁ and R3 areindependently selected from a linear or branched alkyl group having fromone to about four carbon atoms, each of which can optionally bepartially or fully fluorinated.

The non-fluorinated and partially or fully fluorinated β-ketoimineligands of the present invention are represented by the Formula:##STR6##

R₁ and R₃ are independently selected from a linear or branched alkyl oralkenyl group having from 1 to about 8 carbon atoms, each of which canoptionally be partially or fully fluorinated;

R₂ is a hydrogen atom, or a linear or branched alkyl or alkenyl grouphaving from 1 to about 8 carbon atoms, each of which can optionally bepartially or fully fluorinated; and

R₄ is selected from an alkyl, aryl, aralkyl or hydroxyalkyl group havingfrom 1 to about 10 carbon atoms. each of which can optionally bepartially or fully fluorinated.

A preferred method for preparing the β-ketoimine ligands disclosed inFormula V, particularly the partially or fully fluorinated β-ketoimineligands, is disclosed in U.S. Ser. Nos. 270,719 and 283,418, filed onNov. 14, 1988 and Dec. 12, 1988, respectively, the Specifications whichare specifically incorporated by reference herein. In a preferredembodiment, R₁ and R₃ are independently selected from a linear orbranched alkyl group having from one to about four carbon atoms, each ofwhich can optionally be partially or fully fluorinated. The β-ketoiminesare prepared by treating the corresponding β-diketone with potassiumhydride under conditions sufficient to produce the potassium salt of thediketone and subsequently reacting the resultant potassium salt of thediketone with a silylchloride such as tert-butyldimethylsilylchloride toproduce a silylenolether having the general formula: ##STR7##

R₉ is an linear or branched alkyl group having from 1 to about 4 carbonatoms. The silylenolether described above is then treated with a primarymonoamine, R₃ NH₂, wherein R₃ is defined above, to produce the desiredβ-ketoimine.

The non-fluorinated and partially or fully flourinated bridgedβ-ketoimine ligands of the present invention are represented by theFormula: ##STR8##

R₁ and R3 are independently selected from a linear or branched alkyl oralkenyl group having from 1 to about 8 carbon atoms, each of which canoptionally be partially or fully fluorinated;

R₂ is a hydrogen atom, or a linear or branched alkyl or alkenyl grouphaving from 1 to about 8 carbon atoms, each of which can optionally bepartially or fully fluorinated;

R₅, R₆ and R₇ are independently selected from a linear or branched alkylor alkenyl group having from 1 to about 8 carbon atoms, each of whichcan optionally be partially or fully fluorinated; and

R₈ is a linear or branched alkylene, alkenylene,phenylene,alkylphenylene or hydroxyalkylene group having from 1 to about 8 carbonatoms, each of which can optionally be partially or fully fluorinated.

A preferred method for preparing the bridged β-ketoimine ligandsaccording to Formula VI is described in U.S. Ser. No. 283,418. Theseligands are prepared by treating the corresponding β-diketone withpotassium hydride under conditions sufficient to form the potassium saltof the diketone and subsequently reacting the resultant potassium saltof the diketone with a silylchloride such astert-butyldimethylsilylchloride to produce a silylenolether representedby formula IVa. The silylenolether is then treated with two equivalentsof a primary diamine, NH₂ R₃ NH₂ wherein R₃ is defined above to producethe desired bridged β-ketoimine. In a preferred embodiment, R₁ and R₃are independently selected from a linear or branched alkyl group havingfrom one to about four carbon atoms, each of which can optionally bepartially or fully fluorinated.

The ligands of the present invention can exist in two tautomeric forms,keto and enol, the structure of the enol form which is easilyascertained by those skilled in the art. Reference to the keto form ofthe above-mentioned ligands of this invention shall also expresslyinclude the corresponding enol form.

Carrier gases suitable for practicing the process include any gas whichis capable of carrying the defined ligands in the vapor phase forsubsequent reaction with the metal species. The carrier gases must notbe capable of reacting with the ligands or metal species. Such gasesinclude argon, nitrogen, helium and perfluorinated hydrocarbons such asMultifluor APF-200 perfluoroisopropyldecalin which is commerciallyavailable from Air Products and Chemicals, Inc., Allentown, Penna. Thepreferred carrier gas is nitrogen.

The above-mentioned ligands can be utilized in the present process byintroducing the same into a gaseous fluxing atmosphere or byincorporating the ligand into a solder-vehicle mixture such as solderingpaste or cream. The fluxing agents of the present invention can beapplied according to the instant process by both machine and manualoperation. The fluxing agents of the present invention are suitable foruse in foam, wave, dip, spray and brush fluxing operations. The foam,wave and dip fluxing techniques are typically utilized with circuitboards having plated holes because these techniques provide a continuouslayer of fluxing agent onto the solder side of the board therebypromoting capillary penetration of the fluxing agent into the holes. Theparticular fluxing agent to be utilized and the appropriate vehicle fordelivering the fluxing ligands to the workpieces will depend uponnumerous factors including the properties of the circuit board, theelectronic devices to be inserted onto the board and the configurationof the devices on the board.

For mass soldering, the fluxing agent may be applied to the workpiecesin liquid form wherein the β-diketone or β-ketoimine ligand is mixedwith a suitable solvent, preferably a solvent which will leaveessentially no residue on the workpiece to be soldered. Foam flux istypically generated by forcing low-pressure air through an aerator togenerate fine bubbles which are guided to the surface of the boards. Theboards or workpieces to be soldered are passed across the nozzle so thatthe surface to be fluxed contacts the foam and the bubbles burst therebyapplying an even coating of flux onto the workpiece.

The fluxing agent can be applied using a standing wave to form adouble-sided wave which promotes coverage of the workpiece to be fluxedwith the fluxing agent. Likewise, fluxing agent may be applied to theworkpiece by dipping, brushing or spraying the workpiece with fluxingagent. Moreover, the process is well suited for use in reflow solderingprocesses wherein previously applied solder is remelted to form solderedjunctions.

The fluxing agents according to the present process may be dispersed ina soldering cream or paste or may be mixed in a liquid or gaseousvehicle. Soldering cream is a suspension of solder alloy powderparticles and the fluxing ligands to which additional components may beadded. The alloy particles coalesce to form one volume of metal when thesoldering paste containing the fluxing agent is heated to a temperatureabove the melting temperature of the soldering alloy. Typical solderingpastes contain about 75 to 85 mass percent of solder metal whichcorrelates to about 25 to 40 volume percent. Typically, from 0.1% toabout 2.0% of the above-mentioned ligands are dispersed in the solderingpaste.

Other compounds may be added to the fluxing agent, including but notlimited to, activators, foaming agents such as non-ionic surface activeagents; wetting agents and stabilizers. However, since the use of suchadditives may impair the volatility of the metal-ligand complexes aswell as promote corrosivity, such additives should be used withdiscretion.

In order to more fully describe the practice of the present process, twogeneral embodiments of the instant process for fluxing an article to besoldered will be discussed. More particularly, a gaseous fluxing methodand solder paste method for applying the fluxing agents of the presentinvention onto the surfaces of the workpieces to be fluxed will now beexplained.

The gaseous fluxing embodiment comprises preparing printed circuit boardto be fluxed with an additional 5 mil eutectic solder plated on thepads. The electrical components to be soldered onto the circuit boardcan be attached manually or by an automated process utilizingconventional adhesives known in the art. The printed circuit assembly isthen placed into an infrared furnace, vapor phase machine or othersuitable furnace typically used in solder reflow processes and heated toabout 200° to 300° C. The desired β-diketone or β-ketoimine which isdispersed in an inert vehicle as disclosed herein (i.e., nitrogen andthe like) is passed into the hot zone of the furnace by conventionaltechniques. The ligand-saturated vehicle is continuously orintermittently delivered into the furnace. The β-diketone ligands havebeen experimentally shown to react with commonly occurring oxides (CuO,Cu₂ O, PbO, SnO and the like) typically residing on the surface ofcomponents to be soldered. The resultant reaction products have beenanalytically identified as Cu(hfac)₂, Pb(hfac)₂ and Sn(hfac)₂.respectively. Such products are of sufficient volatility such thatfollowing sublimation essentially no residue remains on the workpieces.

The use of the above-mentioned gas-phase fluxing process essentiallyeliminates flux residues associated with conventional processes becausethe metal-ligand complexes formed are extremely volatile under typicalfluxing conditions. This exhibited volatility causes the resultantmetal-ligand complex to sublime to afford a residue-free workpiece. Theoptimum concentration for maximum fluxing action in a carrier gas variesdepending upon the particular fluxing ligand used and the metals to befluxed. Typical concentrations range from 1.0% to about 15.5%. In apreferred embodiment, from 4.6 to 5.2% hexafluoroacetylacetone in anitrogen carrier is utilized. If the ligand concentration in nitrogen isless than about 4.6% a decreased fluxing action is observed.

The above-mentioned embodiment represents a significant advance ingas-phase fluxing processes. Prior to the present invention, gas-phasefluxing processes were believed not to be suitable for use at typicalreflow temperatures (190° to 230° C.) which are needed for theproduction of electronic printed circuit board assemblies. Thisgas-phase fluxing embodiment offers numerous advantages overconventional processes in that the above-mentioned ligands easilysaturate a nitrogen stream; such fluxing agents react exclusively withthe metal oxides of interest without the aid of a catalyst; and formreaction products which are of sufficient volatility as to leaveessentially no residue on the workpieces thereby obviating the need forpost-cleaning using solvents such as chloro-fluorocarbons.

The second embodiment of the process relates to the use of theabove-mentioned ligands dispersed in a conventional soldering paste orcream. An appropriate powdered metal alloy deemed necessary for theparticular soldering application is chosen as is known in the art. Avehicle such as an inert perfluorochemical of desired viscosity andvapor pressure is chosen such that the powdered metal alloy-vehiclemixture is acceptable for stencil application onto the workpiece. Thevehicle components should also be capable of evaporating or sublimingprior to alloy reflow. An appropriate β-diketone or β-ketoimine ligandfluxing agent as disclosed herein is then incorporated into thealloy-vehicle mixture. The ligand may be loosely coordinated with anappropriate lewis base (e.g., dimethyl amine) to enhance ligandperformance. The alloy paste is then stencil printed onto the pads ofthe circuit board to be soldered by automated or manual techniques knownin the art and the assembly is placed into an infrared or other suitablefurnace used in the soldering process. Following formation andsublimation of the metal-ligand complexes formed by reaction of thefluxing agent with metal oxides residing on the surface of theworkpiece, the assembly is removed from the oven. Post cleaning is notrequired prior to soldering components onto the printed circuit board.

Process conditions for both the gas-phase and paste embodiments aresimilar to conventional reflow processes. The preferred operatingtemperature is comensurate with that used in conventional processes andtypically ranges from about 200° to about 230° C. The optimum reactiontime will vary depending upon the particular ligand used in the process.Typical times range from about 6 to 10 minutes. Shorter reflow times(i.e., <5 minutes) have been found to decrease fluxing effectiveness.Furnace pressure typically ranges from about 0 to 1.5 psig.

The following examples are provided to further illustrate variousembodiments of the present invention and are not intended to restrictthe scope of the invention. In the following examples, temperatures areset forth uncorrected in degrees Celcius.

EXAMPLE 1 Gas-Phase Fluxing With Hexafluoroacetylacetone Dispersed inNitrogen

A printed circuit board, a FR-4 glass-epoxy substrate with 95% Sn/ 5% Pbsolder coated integrated circuit packages and 1206 cap lands fabricatedwith 8 mil solder bumps to approximate a typical volume of solder at aparticular solder Joint, was obtained from Microcircuit EngineeringCorporation, Mount Holly, N.J. The substrate, integrated circuits andchip capacitors were previously aged to afford varying degrees ofsolderability. The aging conditions explored were unaged, 24-hour steamaging and 155° C. dry air aging. The aged components were glued to theprinted circuit board and placed into a stainless steel tube furnacewhich was evacuated and heated to 218° C. Nitrogen gas (house linehaving about 5 ppm O₂) was passed through a bubbler containinghexafluoroacetylacetone purchased from Strem Chemicals, Inc.,Newburtport, Mass. and the circuit board was subjected to a 12.1%hexafluoroacetylacetone/nitrogen atmosphere for a period of ten minutes.Following removal from the oven, a soldered connection of excellentquality was obtained between the circuit board the individualcomponents. No residue on the circuit board was detected by visualinspection.

EXAMPLE 2 Gas-Phase Fluxing with Hexafluoroacetylacetone in Nitrogen

In a procedure similar to Example 1, about 25 g of solder powder(Sn63/Pb37) which had been air oxidized at ambient temperature for fiveweeks was subjected to a hexafluoroacetylacetone fluxing atmosphere. Thefluxed powder was then heated to 215° C. wherein reflow occurred in theabsence of a residue. In contrast, a control sample prepared bysubjecting the solder powder to only a nitrogen atmosphere exhibited noreflow.

Representative ligands suitable for use in the present invention aredisclosed below wherein the chemical structure and both the IUPAC andabbreviated names of the ligands are provided. ##STR9##

Having thus described the present invention, what is now deemedappropriate for Letters Patent is set out in the following appendedclaims.

We claim:
 1. A process for fluxing an article having at least a portionof a surface coated with a metal species comprising contacting theportion of the article to be fluxed with an effective amount of aβ-diketone or β-ketoimine ligand at at temperature sufficient to form ametal-ligand complex on the surface of the article to be fluxed andremoving the resultant metal-ligand complex from the surface of thearticle by sublimation rendering the surface of the articlesubstantially free of the surface coating.
 2. The process according toclaim 1 wherein the ligand is represented by the formula: ##STR10## R₁and R₃ are independently selected from a non-fluorinated, partiallyfluorinated or fully fluorinated linear or branched alkyl or alkenylgroup having from 1 to about 8 carbon atoms;R₂ is a hydrogen atom, anon-fluorinated, partially fluorinated or fully flourinated linear orbranched alkyl or alkenyl group having from 1 to about 8 carbon atoms;and Y is selected from an oxygen atom; N-R₄ wherein R₄ is selected froma non-fluorinated, partially fluorinated or fully fluorinated alkyl,aryl, aralkyl or hydroxyalkyl group having from 1 to about 10 carbonatoms; or Y is ##STR11## R₅, R₆ and R₇ are independently selected from anon-fluorinated, partially fluorinated or fully fluorinated linear orbranched alkyl or alkenyl group having from 1 to about 8 carbon atomsand R₈ is a non-fluorinated, partially fluorinated or fully fluorinatedlinear or branched alkylene, alkenylene, phenylene, alkylphenylene orhydroxyalkylene group having from 1 to about 8 carbon atoms.
 3. Theprocess according to claim 2 wherein the metal species is a metal oxiderepresented by the formulae MO, MO₂, MO₃, M₂ O, and M₂ O₃.
 4. Theprocess according to claim 2 further comprising mixing the β-diketone orβ-ketoimine ligand of step (a) with a carrier prior to contacting theregion of the article to be fluxed with an effective amount of aβ-diketone or β-ketoimine ligand.
 5. The process according to claim 4wherein the carrier is selected from argon, nitrogen, helium andperfluorinated hydrocarbons.
 6. The process according to claim 5 whereinthe perfluorinated hydrocarbon is perhydrophenanthrene.
 7. The processaccording to claim 4 wherein the carrier is soldering plate.
 8. Aprocess for fluxing an article having at least a portion of a surfacecoated with a metal species comprising:(a) contacting the region of thearticle to be fluxed with an effective amount of a β-diketonerepresented by the formula ##STR12## R₁ and R₃ are independentlyselected from a non-fluorinated, partially fluorinated or fullyfluorinated linear or branched alkyl or alkenyl group having from 1 toabout 8 carbon atoms; R₂ is selected from a hydrogen atom, anon-fluorinated, partially fluorinated or fully fluorinated linear orbranched alkyl or alkenyl group having from 1 to about 8 carbon atoms;(b) at a temperature sufficient to form a metal-ligand complex on thesurface of the article to be fluxed; and removing the resultantmetal-ligand complex from the surface of the article by sublimationrendering the surface of the article substantially free of the surfacecoating.
 9. The process according to claim 8 wherein the metal speciesis a metal oxide represented by the formulae MO, MO₂, MO₃, M₂ O, and M₂O₃.
 10. The process according to claim 8 wherein R₁ and R₃ areindependently selected from a linear or branched alkyl group having from1 to 4 carbon atoms.
 11. The process according to claim 8 wherein theligand is selected from 1,1,1,5,5,5-hexafluoro-2,4-pentanedione,1,1,1-trifluoro-2,4-pentanedione, 2,2,6,6-tetramethyl-3,5-heptanedioneand 1,1,1,5,5,6,6,7,7,7,-decafluoro-2,4-heptanedione.
 12. A process forfluxing an article having at least a portion of a surface coated with ametal species comprising:(a) contacting the region of the article to befluxed with an effective amount of a β-ketoimine ligand represented bythe formula ##STR13## R₁ and R₃ are independently selected from anon-fluorinated, partially fluorinated or fully fluorinated linear orbranched alkyl or alkenyl group having from 1 to about 8 carbon atoms;R₂ is a hydrogen atom, a non-fluorinated, partially fluorinated or fullyfluorinated linear or branched alkyl or alkenyl group having from 1 toabout 8 carbon atoms; and R₄ is selected from a non-fluorinated,partially fluorinated or fully fluorinated alkyl, aryl, aralkyl orhydroxyalkyl group having from 1 to about 10 carbon atoms; (b) at atemperature sufficient to form a metal-ligand complex on the surface ofthe article to be fluxed; and removing the resultant metal-ligandcomplex from the surface of the article by sublimation rendering thesurface of the article substantially free of the surface coating. 13.The process according to claim 12 wherein the metal species is a metaloxide represented by the formulae MO, MO₂, MO₃, M₂ O, and M₂ O₃.
 14. Theprocess according to claim 12 wherein R₁ and R₃ are independentlyselected from a linear or branched alkyl group having from 1 to 4 carbonatoms.
 15. The process according to claim 12 wherein R₁ and R₃ areindependently selected from a linear or branched alkyl group having from1 to about 4 carbon atoms of which is partially or fully fluorinated.16. The process according to claim 8 wherein the ligand is selected from4-(2,2,2,-trifluoroethyle)imino-1,1,1,5,5,5,-hexafluoro-2-pentanone,5-(2,2,2-trifluoroethyle)imino-1,1,1,2,2,6,6,6,-octafluoro-3-hexanone,6-(2,2,2,-trifluoroethyl)imino-(b1,1,1,2,2,3,3,7,7,7,-decafluoro-4-heptanone and4-(phenyl)imino-1,1,1,5,5,5-hexafluoro-2-pentanone.
 17. A process forfluxing an article having at least a portion of a surface coated with ametal species comprising:(a) contacting the portion of the article to befluxed with an effective amount of a β-ketoimine ligand represented bythe formula: ##STR14## R₁ and R₃ are independently selected from anon-fluorinated, partially fluorinated or fully-fluorinated linear orbranched alkyl or alkenyl group having from 1 to about 8 carbon atoms;R₂ is a hydrogen atom, or a non-fluorinated, partially fluorinated orfully fluorinated linear or branched alkyl or alkenyl group having from1 to about 8 carbon atoms; R₅, R₆ and R₇ are independently selected froma non-fluorinated, partially fluorinated or fully fluorinated linear orbranched alkyl or alkenyl group having from 1 to about 8 carbon atoms;and R₈ is a non-fluorinated, partially fluorinated or fully fluorinatedlinear or branched alkylene, alkenylene, phenylene, alkylphenylene orhydroxyalkylene group having from 1 to about 8 carbon atoms; (b) at atemperature sufficient to form a metal-ligand complex on the surface ofthe article to be fluxed; and removing the resultant metal-ligandcomplex from the surface of the article by sublimation rendering thesurface of the articled substantially free of the surface coating. 18.The process according to claim 17 wherein the metal species is a metaloxide represented by the formulae MO, MO₂, MO₃, M₂ O, and M₂ O₃.
 19. Theprocess according to claim 17 wherein R₁ and R₃ are independentlyselected from a linear or branched alkyl group having from 1 to 4 carbonatoms.
 20. The process according to claim 17 wherein R₁ and R₃ areindependently selected from a linear or branched alkyl group having from1 to about 4 carbon atoms of which is partially or fully fluorinated.